I am a former sailor returning to the sport (after 15 yrs) now that children are in their teens. I purchased a '77 C-27 (Dinette layout) this time last year. I did my own inspection after thoroughly researching "what to look for". Here's what I've found:
1) Bottom Blisters. I found hundreds once I got the layers of old caked on bottom paint off. I could not see nor feel them during the inspection. I have now spent a year (mostly limited to 4-8 hrs a week) repairing this. Although not complicated nor expensive, the repair is extensive for the do-it-yourselfer. It would be very expensive at a yard (more than the value of the boat).
2) Deck Hardware leaks: This one can be minimal, or it can get extensive. My chainplates had been leaking thru the deck. Bottom line: I'm replacing the original rotted main bulkheads with teak faced mahogany marine ply. Additionally, I will be re-bedding most all deck hardware.
This one can go deep as deck core can easily be rotted out too. One does not want to get involved in re-coring a deck. Well, I don't anyway (it's a big job).
3) Closely inspect standing rigging. I got lucky here.
4) Running rigging / blocks / sheaves. I'm replacing all mine and going to all line halyards (no wire). Catalina has a kit for this. While at it, I too want all lines led aft for simplification of single handing.
Bottom line: Happily pay for a survey. Money very well spent.
I absolutely love my C-27 and cannot wait to get her back in the water where she belongs. I enjoy doing the work and have a hobie cat to satisfy immediate sailing requirements. While I'm doing this, I am upgrading most everything. Visit www.catalina.com
for loads of info. One more note: Catalina is still in existence. This is huge! I have called the factory for advice on a number of issues. They are extremely helpful, will provide loads of info on your specific boat, and still have replacement parts, upgrades, etc. Some of the best customer service I have come across in todays economy.
Great choice for a daysailor, coastal cruiser.